Which Covid-19 (Coronavirus) Vaccine Will You Take?

Finally, there is a glimmer of hope, or shall we say several, in the global fight against COVID-19 that has infected more than 62 million people and claimed more than 1.4 million deaths to date. We are approaching that light at the end of the tunnel armed with 3 great COVID-19 (coronavirus) vaccines, thus far, to help us tame this pandemic.

Both Pfizer/BioNTech and Moderna had announced that their vaccines are 95% and 94.5% effective, respectively, in preventing COVID-19 based on their interim data. Among the participants who received Moderna’s placebo (no vaccine, control group), 11 became severely ill, but none of the participants who received the actual vaccine became severely ill, including those who are older adults—which is remarkable given that the older adults are quite vulnerable to more serious infection from COVID-19. The outcomes from both mRNA vaccines indicate that they can induce the kind of immune response that protects people when exposed to the coronavirus. Both studies did a good job recruiting a reasonably diverse group of participants including Hispanic or Latinx, Black or African American, as well as people older than 65, and people with high-risk chronic diseases—which is important in determining how the vaccines will perform in different population.

Additionally, AstraZeneca’s vaccine proved to be 70% efficacious according to their Phase III (large) clinical study interim outcome and could be 90% effective by tweaking the dosing. AstraZeneca reports its vaccine prevented coronavirus infection 62% of the time after giving two doses, 4 weeks apart. However, in a subgroup of participants who received a half-dose followed by a full dose 4 weeks later, the vaccine appeared to be 90% effective, although that was only true in a much smaller number of participants. This averaged out to 70% overall efficacy.

Meanwhile, Gamaleya Research Institute, part of Russia’s Ministry of Health, claimed that its Sputnik V demonstrated 92% efficacy based on results from 20 participants in the trial who developed Covid-19 after receiving either the vaccine or a placebo (no vaccine). Very little scientific data was made available to objectively assess their data, and it is difficult to make any reasonable conclusion from the 20 cases with no detail—not even the study protocol!

Given these many choices, it is only human nature that we tend to compare and contrast the different options for vaccination. Although I must caution you that while some attributes of these vaccines can be analyzed side-by-side, others should not be directly compared--unless the vaccine candidates are compared head-to-head in a singular study. Namely, safety and efficacy results should not be directly compared from different studies because the study parameters usually vary between the clinical trials. For instance, the Moderna and Pfizer studies used slightly different protocols. For it to count as a COVID-19 case, participants in the Moderna study required at least two symptoms of the disease along with a positive test for the coronavirus. In contrast, the Pfizer study had to only have one symptom for it to count as a COVID-19 case. Furthermore, while Moderna waited 14 days following the booster (2nd) shot to start counting cases; Pfizer began counting at seven days post 2nd dose. Keeping this in mind, take a look at the table below analyzing 4 frontrunner COVID-19 vaccines.

Created by VaxTherapy Sources: clinicaltrials.gov, trial websites, and company press releases — Created by VaxTherapy
Sources: *clinicaltrials.gov, trial websites, and company press releases*

Also, keep in mind that the efficacy results will be refined as additional data roll out in the months ahead. Another point to keep in mind is that some study participants who were infected might not have shown any symptoms; these people could not be counted in the reported cases in these trials—which potentially overestimated the efficacy results. Still, in the world of vaccines, these efficacy numbers are superb in terms of preventing symptomatic infections. For perspective, the FDA had set its efficacy requirement at 50% for the COVID-19 vaccines, and last year’s flu vaccine was 29% effective according to the Centers for Disease Control and Prevention (CDC).

While AstraZeneca's 70% average efficacy was significantly lower than the Moderna and Pfizer vaccine efficacies, this vaccine could prove to be more valuable globally, leading the way for vaccine coverage in poorer countries where it is in dire need. Pfizer's and Moderna's vaccines use very similar mRNA technology, while AstraZeneca uses a genetically modified viral vector. mRNA vaccines lend themselves to quick turnaround from a development standpoint, but mRNAs are fragile and unstable in nature, so they are encased in lipid nanoparticles; you can think of these as buttery substances that can melt at room temperature.

Hence the mRNA vaccines must be kept at cold temperatures, requiring special equipment to store and ship these vaccines. Pfizer's vaccine has to be kept at ultracold temperatures of -100°F (-70°C). Moderna’s vaccine, with a different formulation of the lipid nanoparticles, can be shipped at -20°C (-4°F) and can be kept stable for 30 days at 2 to 8°C (36 to 46°F), the temperature of a standard home refrigerator. On the other hand, viral vector vaccines are cheaper to produce, as in the case of the AstraZeneca vaccine, and it can be kept stable for six months at standard refrigerator temperatures—ideal for global distribution, particularly in poorer countries.

Disclaimer: Vaxtherapy is NOT affiliated with any of the pharma/biotech companies working on COVID-19 vaccines. The purpose of this post is to provide education and awareness from a virologist’s independent perspective based on available facts and data.

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